A fiber-reinforced plastic (FRP) is a material produced by binding reinforcing fibers (e.g., glass fibers and carbon fibers) using a resin. The FRP is a composite material that exhibits excellent mechanical strength, heat resistance, formability, and the like. Therefore, the FRP is widely used in a wide variety of fields including the airplane industry, the space industry, the vehicle industry, the building material industry, the sports industry, and the like.
In particular, a carbon fiber-reinforced plastic (CFRP) is characterized by high strength and reduced weight. For example, a thermosetting epoxy resin is mainly reinforced using carbon fibers, and is used as a structural material for producing an airplane. Meanwhile, in recent years, an FRP using a thermoplastic resin has attracted attention because the FRP has such a feature that a forming cycle can be reduced in addition to the above-mentioned characteristics.
In the FRP using the thermoplastic resin as described above, use has been made of continuous fibers as the reinforcing fibers in order to obtain sufficient mechanical strength (see, for example, Patent Literatures 1 and 2). Use has also been made of carbon long fiber-reinforced resin pellets obtained by impregnating carbon long fibers with a thermoplastic resin while aligning the carbon long fibers under tension, and then cutting the resulting fiber-reinforced resin rod (strand) to an arbitrary length (see, for example, Patent Literature 3). A method involving impregnating a mat formed of fibers (non-woven fabric or the like) with a thermoplastic resin to produce a CFRP has also been investigated (see, for example, Patent Literature 4).